Combination main burner and after burner fuel pump



Feb. 28, 1961 J. F. MURRAY 2,972,952

COMBINATION MAIN BURNER AND AFTER BURNER FUEL PUMP Filed May 18, 1955 3Sheets-Sheet 1 IN VEN TOR.

JOHN F. MURRAY Feb. 28, 1961 J. F. MURRAY 2,972,952

COMBINATION MAIN BURNER AND AFTER BURNER FUEL PUMP Filed May 18, 1955 3Sheets-Sheet 2 JOHN F. MURRAY ATTORNEYS Feb. 28, 1961 J. F. MURRAY2,972,952

COMBINATION MAIN BURNER AND AFTER BURNER FUEL PUMP Filed May 18, 1955 3Sheets-Sheet 3 R ii -8 00 J Q 1 Q 1 a 1 q 0% an O 0 c 9 0 CO /I\ 3\$ a"I B 8 R W 2 a --R U a: 3 8 N N p N m 9 N INVENTOR.

JOHN F. MURRAY ATTORNEYS United States Fatent COMBINATION MAIN BURNERAND AFTER BURNER FUEL PUMP John F. Murray, Macedonia, Ohio, assignor toThompson Ramo Wooldridge Inc., a corporation of Ohio Filed May 18, 1955,Ser. No. 509,313

10 Claims. (Cl. 103-4) This invention relates generally to pumps andmore particularly relates to a combination pump of the type utilized inan aircraft fuel system wherein three separate pumping units areprovided, two of the pumping units comprising an after burner pump and amain burner pump discharging to separate points of utilization and thethird pump unit constituting a supplemental pump discharging fluid to atransfer device having means formed to parallel selectively thedischarge of the third pump with the discharge of the first and secondpump units, respectively.

Briefly described, the present invention relates to a pressure-loadedmultiple gear pump. A pump casing or housing is provided with aplurality of pumping cavities housing a corresponding plurality ofrotary fluid-displacement means. For example, three sets of intersectingbores are provided in the exemplary construction herein described andthree separate sets of rotary gears move fluid from an inlet on one sideof each respective pumping cavity to an outlet on the other side of eachrespective pumping cavity. The pump further includes a volute pumpingchamber in which is rotated a centrifugal impeller so that fluid at theinlet of the pump may be initially pressurized and supplied to therespective inlets of the gear pumping units, thereby reducing inletlosses.

According to the present invention, the pump incorporates a flowtransferring means in the casing of the pump for selectively parallelingpairs of outlets. For example, the three outlets of the gear pumpingunits comprise threelongitudinally spaced openings selectivelycontrolled by a valve having opposed spaced apart piston controlportions each respectively adapted to close one of the end openings ofthe outlet. Whenever one of the end openings is closed, the other endopening will be in parallel with the middle opening. Thus, one of thepumping units advantageously supplies fuel to the main burners of -a jetengine and the other pumping unit supplies fuel to the after burners ofthe jet engine, the third pumping unit having its discharge selectivelydirected in parallel with either the main burner pumping unit or theafter burner pumping unit.

The transfer valve embodies a spring which operates as a control springto bias the valve in one direction, thereby biasing the valve in onedirection.

The transfer valve is further provided with a motive surface subjectedto fluid at pressures generated by the main burner pumping unit. Theforce thus generated is applied to the valve in a direction opposite thethrust imparted to the valve by the control spring. Accordingly, whenthe pump is idle the valve will be biased by the coil spring in onedirection to parallel the main burner pumping unit and the supplementalpumping unit. Upon operation of the pump, the pressure acting againstthe motive surface of the valve will build up to a predetermined value,whereupon the valve will be moved aginst the bias of the spring and thesupplemental pump will be placed in parallel with the after burnerpumping unit.

If for any reason such as mechanical failure, jamming 2,972,952 PatentedFeb. 28, 196i ice or other interferences with pump operation the mainburner pumping unit should fail to maintain a predetermined value ofpressure against the motive surface, the coil spring will again move thevalve so that the discharge of the supplemental pumping unit will bedirected to the point of utilization normally served by the main burnerpumping unit.

It is an object of the present invention, therefore, to provide acombination main burner and after burner fuel pump havingflow-transferring means which are pressure-responsive.

Another object of the present invention is to provide a combinationmultiple pump unit having flow transfer means which will insure a supplyof fluid to separate points of utilization.

Yet another object of the present invention is to provide a transfervalve for a multiple pump which will selectively parallel differentpairs of pumping unit outlets in response to variations in a pressurecondition.

Many other objects, advantages and additional features of the presentinvention will become manifest to those versed in the art upon makingreference to the detailed description which follows and the accompanyingsheets of drawings in which a preferred structural embodimentincorporating the principles of the present invention is shown by way ofillustrative example.

On the drawings:

Figure 1 is an end elevational view of a pump provided in accordancewith the principles of the present invention;

Figure 2 is a cross-sectional view taken substantially on line I'III ofFigure 1;

Figure 3 is an enlarged fragmentary cross-sectional view illustratingadditional details of construction of the flow-transferring meansprovided in accordance with the principles of the present invention; and

Figure 4 is a diagrammatic plumbing diagram illustrating the paths offluid flow in connection with a pump provided in accordance with theprinciples of the present invention.

As shown on the drawings:

The pump of the present invention is indicated generally by thereference numeral 10 and comprises a casing or housing 11 whichconstitutes a plurality of connected housing parts identified on Figure2 from left to right by the reference numerals 12, 13, 14, 15 and 16.

The housing part indicated at 15 has a mounting pad 17 from whichprojects a plurality of threaded studs 18 by means of which the pump maybe connected to a con duit for supplying fluid to the pump inlet formedin the housing part 15 and indicated by the reference numeral 19. Thereis further provided in the housing part 15 a volute pumping chamber 20in which is rotated a centrifugal impeller 21.

The housing parts 12, 13, 14 and 15 together form three longitudinallyspaced pumping cavities for three separate gear pumping units indicatedgenerally by the reference characters A, B and C, respectively.

Before proceeding with the further description of the structural detailsof the pump 10, reference can be advantageously made to the plumbingdiagram of Figure 4 wherein is illustrated the environment in which thepump 10 finds particular utility.

First of all, there is indicated at 22a fuel cell from which fluid issupplied to the inlet 19, initial pressurization of the fluid beingeffected by the centrifugal impeller 21 in the volute pumping chamber20. The centrifugal pumping unit discharges through a strainer indicateddiagrammatically at 23 to a common inlet supplying each of the gearpumping units A, B and C.

The pumping unit A discharges to a main burner control indicated at 24and the fuel is supplied to the main burners 26 of an aircraftpropulsion engine utilizing jet burners. A by-pass 27 from the mainburner control 24 takes excess fuel not required at the burners 26 to apoint interstage of the pump 10, namely, a point between the centrifugalimpeller 21 and the gear pumping units A, B and C.

Fluid from the gear pumping unit C is supplied to an after burnercontrol 28 which controls the supply of fuel to the burners 29 of theafter burner portion of the jet engine. A by-pass 30 carries excess fuelnot required by the after burners 29 from the after burner control 28 toa point interstage of the pump 10, namely, a point intermediate thecentrifugal impeller 21 and the gear pumping units A, B and C.

The third gear pumping unit B discharges to a flowt'ransferring meansindicated generally by the reference numeral 31, the flow-transferringmeans operable to selectively parallel the discharge of the thirdpumping unit B with the discharge of the first and second gear pumpingunits A and C, respectively.

As will be explained in greater detail hereinafter, it will be notedthat the flow-transferring means 31 has one end thereof vented as at 32to discharge pressure from the pumping unit A and the opposite end isvented as at 33 to interstage pressure corresponding to the pressure onthe inlet side of the gear pumping units A, B and C.

Each of the gear pumping units A, B and C are substantially identicalwith respect to structural features, and, accordingly, common referencenumerals will be used wherever possible.

Each gear pumping unit comprises a driven gear 34 meshing at an area'ofintermesh 36 with a driver gear 37.

Extending axially outwardly from the hub portion of each respectivedriver and driven gear is a first shaft extension 38 and a second shaftextension 39. Each shaft extension 38 is journaled by a stationarybushing member 40 received in 'a corresponding housing bore and having aflange '41providing a sealing face for engaging and sealing against theadjoining side face of the gear.

Each gear shaft extension 39 is journaled in the casing by a movablepressure-loaded bushing 42 having a flange 43 providing a front face 44for engaging and sealing against an adjoining gear side face and a rearface 46 which together with means including the housing 11 forms apressure control chamber 47 communicating with pump-generated dischargepressure to pressure load the movable bushing42'into'sealingrelationship against the side face of the gear.

The housing part 12 is closed by a cover member 48 assembled in firmassembly to the housing part 12 by a plurality of fasteners 49. A shaftdriving member 50 has a splined portion 51 adapted to be connected to aprime mover on the outside of the pump and extends inwardly intothehousing part 12 for connection to the gear pumping units A, B and C.The driving member 50 has acollar portion 52 splined to a quill shaft 53which extends through hollow portions of the driver gears 37 of the gearpumping units A and B. The quill shaft 53 is in turn splined tothedriver gear of the gear pumping unit C and also to a second quill shaftmember 54 which extends through the gear pumping unit C and has attachedthereto at one end a gear 56 forming part of a gear train 57 driving thecentrifugal impeller 21. Thus, the gears of the gear pumping units A, Band C are rotated at a speed corresponding'to arated efficiency speedfor intermeshing gears and the centrifugal impeller 21 is rotated at amuch higher speed corresponding to the speed for greatest ratedefficiency of centrifugal impellers. The cover member 16 is fastened tothe housing part by a plurality of fasteners indicated at 58, therebyenclosing the gear train 57 and closing the end of the pump housing 11.p

The shaft extensions and the hubs of the driver gears 37 are hollow and'thes'haft extensions38*and-39" as 4 well as the hub portions of thedriven gears 34 are also hollow, thereby providing through passages thelength of the pump housing 11. Thus, all of the internal cavities suchas the cavity 59 in the pump housing 11, which are separated from theactual outlet portions of the pump can be communicated with a source oflow pressure such as the pump inlet to facilitate the use of lowpressure seals for minimization of leakage and other sealing problems.

Moreover, this arrangernnt affords another advantageous structural andfunctional feature, according to the principles of the presentinvention, which permits the flooding and lubrication of a thrustbearing associated with the driving means just described. In referenceto this arrangement, it should be noted on Figure 2 that the drivingmember 50 has a radially outwardly extending annular flange 60characterized by the provision on one face thereof of a chamferedbearing face 61 engaging a ring of bearing material 62 seated in anannular recess 63 formed in the cover member 48. A coil spring 64 .islocated in a recess jointly provided by the driving member 50 and thequill shaft 53 so that one end of the coil spring 64 is bottomed againstthe driving member 50 and the opposite end is bottomed against the quillshaft 53, thereby maintaining a continuous biasing force between the twoparts.

The driving member 50 is provided with an axially extending annular lip66 and the cover member 48 is provided with an additional recess 67 inwhich is mounted a sealing assembly 68, the sealing assembly 68 engagingagainst the lip 66 and effecting an adequate seal between the covermember 48 and the driving member 50. Since the sealing assembly 68 islocated outside of the thrust bearing formed by the flange 60 and thebearing ring 61, the thrust bearing can be flooded with the fluidcontained within the cavity 59 to insure adequate lubrication andcooling even though the pump is operated at high speeds.

Referring now specifically to Figure 3 in conjunction with Figure 2, itwill be noted that each of the pump units A, B and C has a separateoutlet portion indicated by the reference numerals 70, 71 and 72, suchoutlet portions being provided by cored areas or recesses within thehousing part 13. It should be particularly noted that these outletportions 70-, 71 and 72 are in longitudinally spaced relation and arearranged to lie adjacent to and in communication with a tubular bore 73,the outlet portions 70, 71 and 72 constituting annular recesses locatedradially outwardly of the bore 73.

The flow transfer means 31 is received within the bore 73 and comprisesa tubular sleeve 74 abutting at one end against the housing part 14 asat 76 and sealed within the housing part 13 to separate the outletportions 70, 71 and 72 by a plurality of sealing rings 77.

The tubular sleeve member 74 is particularly characterized by theprovision of a central bore 78 communicating in fluid flow relation withthe outlet'portion 71 by a plurality of openings 79.

At opposite ends of the sleeve member 74, there is formed a counterbore80 and 81, respectively, a chamfered shoulder 82 separating the centerbore 78 from the counter-bore 80 and a chamfered shoulder 83 separatingthe center bore 78 from the counterbore 81.

The counterbore 80 has flow communication with the outlet portion 72 bymeans of a plurality of openings 84 formed in the walls of thecounterbore 80 outwardly of the shoulder 82. Likewise, the counterbore81communicates with the outlet portion 70 by means of a plurality ofopenings 86 formed in the bore walls of the counterbore 81 outwardly ofthe shoulder 83.

By virtue of the arrangement thus far described, it will be appreciatedthat the outlet openings 79, 84 and 86 can be selectively paired byclosing either of the'end openings 84 and 86.

'To effect that end, the presentinvention contemplates tl1e provision"of "21 control mechanism-utilizing a valve member indicated generally at87 and having oppositely disposed longitudinally spaced control portionsconsisting of a first piston 88 and a second piston 89 spaced apart fromone another by a shaft member 90.

The piston 88 comprises a head portion chamfered at its peripheral edgeto provide a seating surface 91 engaging the shoulder 83 and a pistonskirt 92 extending axially away from the head portion of the piston 88and engaging the bore Walls of the counterbore 81. When the piston 88 isseated against the shoulder 83, the outlet portion 70 is isolated fromthe outlet portion 71.

In like manner, the piston 89 has a chamfered peripheral edge forming aseating portion 93 adapted to seat and engage the shoulder 82, thepiston 89 further including an axially extending skirt 94 which slidablyen'- gages the bore walls of the counterbore 80. When the piston 89 isseated against the shoulder 82, the outlet portion 72 is isolated fromthe outlet portion 71.

The shaft member 90 has longitudinally spaced shoulders 96 and 97abutting against the head portions of the pistons 88 and 89 andseparated from one another by a spacing dimension greater than thespacing dimension between the outlet openings 84 and 86 so thatpositioning of the valve 87 with either of the seating portions 91 or 93engaged against a corresponding shoulder 82 or 83 will pair the outletopening 79 with one of the outlet openings 84 or 86.

A sealing ring 98 is located between the shaft member 90 and eachrespective piston 88 and 89 and the pistons are retained in assemblywith the shaft member 90 against the corresponding shoulders 96 and 97by appropriate fastening means indicated at 99.

The housing part 14 has a recess 100 disposed longitudinally adjacentthe bore 73 in the housing part 13 to bottom one end of a coil spring101, the other end of the coil spring 101 being bottomed against thehead portion of the piston 89. Thus, a continuous biasing force isexerted against the valve 87 tending to seat the valve seat 93 againstthe shoulder 82 and paralleing the discharge of the pumping unit B withthe discharge of the pumping unit A Whenever the pump 10 is at rest.

In order to facilitate automatic pressure-responsive operation of thevalve 87, however, motive means are provided in accordance with theprinciples of the present invention for effecting automatic operation ofthe flowtransferring device. First of all there is provided a cylindermember 102 which is received in the bore 73 and sealed therein by asealing ring 103. The cylinder member 102 has a bore 104 whichcommunicates as at 105 with the pump discharge of the gear pumping unitA, thereby communicating pump-generated fluid pressure to the bore 104of the cylinder member 102.

Slidably reciprocable within the bore 104 is a piston member 106attached as at 107 to one end of the valve 87. The piston has formed onone end thereof a motive surface 108 which is subjected to the fluidpressures in the bore 104, thereby to impose a thrust force against thevalve 87 tending to move the valve 87 in longitudinal direction againstthe continuous biasing force exerted by the coil spring 101.

After the pump 10 is started, pump-generated pressure will becommunicated to the bore 104 whereupon the build-up of pressure willeventually supply sufficient force to the valve 87 to overcome thecontinuous biasing force exerted by the coil spring 101. When thisoccurs, the valve 87 will move to the right as shown in Figure 3 and thepiston 88 will close off the outlet opening 86 and parallel thedischarge of the gear pumping unit B with the discharge of the gearpumping unit C.

To insure full response of the valve 87 to the pressure forces acting inthe cylinder chamber 104, the spaces behind the pistons 88 and 89 arevented to a zone of low pressure previously indicated in connection withan explanation of the plumbing diagram of Figure 4 as the interstagepressure ahead of the gear pumping units 'A, B

and C. Thus, the cavities 110 in the housing part 14 are vented tointerstage pressure and the shaft 90 has a passage 111 extendingtherethrough to vent this low pressure to the area behind the piston 88.

With the arrangement thus described, it will be appreciated that thepumping unit A can be effectively utilized as a main burner pump, whilethe pumping unit C can be utilized as an after burner pump. Moreover,the third gear pumping unit or pumping unit B functions as asupplemental pump which can be selectively paralleled in response tochanges in a pressure condition. Thus, for starting, pumps A and B arein parallel because the valve 87 is normally biased in one direction bythe control spring. When a predetermined value of discharge pressure isobtained, the valve moves and pumps B and C are paralleled.

This arrangement has an added safety feature since it insures deliveryof fluid to separated points of utilization. For example, if the pump 10is in full operation and pumps B and C are in parallel discharging tothe after burner control 28 and the pump A is discharging to the mainburner control 24, then failure of the pump A because of binding orseizure or some other cause of reduction in discharge pressure willreduce the pressure acting on the motive surface 108 of the piston 106whereupon the valve 87 will be shifted and the discharge from the pump Bwill be directed to the point of utilization previously served by thepump A. In this manner, the pump B operates as a standby main burnerfuel pump.

Although various minor structural modifications might be suggested bythose versed in the art, it should be understood and I wish to embodyWithin the scope of the patent warranted hereon all such modificationsas reasonably and properly come within the scope of my contribution tothe art.

I claim as my invention:

1. In combination, first and second pumps each discharging to separatedpoints of utilization, a third pump having a flow-transferring meansreceiving the discharge thereof, said flow-transferring means comprisinga sleeve having three longitudinally spaced openings, the end openingscommunicating separately with the separated points of utilization, theintermediate opening receiving the discharge of the third pump, a valvereciprocably slidable in said tubular sleeve between spaced portions insaid sleeve and having longitudinally spaced portions for selectivelyclosing off either of said end openings, thereby to selectively parallelthe discharge of the third pump with the discharge of said first andsecond pumps upon movement of said valve to either of said spacedpositions through the intermediate opening and the other of said endopenings.

2. In combination, first and second pumps each discharging to separatedpoints of utilization, a third pump having a flow-transferring meansreceiving the discharge thereof, said flow-transferring means comprisinga sleeve having three longitudinally spaced openings, the end openingscommunicating separately with the separated points of utilization, theintermediate opening receiving the discharge of the third pump, a valvereciprocably slidable in said tubular sleeve between spaced portions insaid sleeve and having longitudinally spaced portions for selectivelyclosing 01f either of said end openings, thereby to selectively parallelthe discharge of the third pump with the discharge of said first andsecond pumps upon movement of said valve to either of said spacedpositions through the intermediate opening and the other of said endopenings, said valve having means providing a motive surface, and meansfor communicating fluid at pressures generated by said first pump tosaid motive surface for moving said valve to one of said positions.

3. In combination, first and second pumps each discharging to separatedpoints of utilization, a third pump having a flow-transferring meansreceiving the discharge thereof, said flow-transferring means comprisinga sleeve having three longitudinally spaced openings, the end openingscommunicating separately with the separated points of utilization, theintermediate opening receiving the discharge of the third pump, a valvereciprocably slidable in said tubular sleeve between spaced portions insaid sleeve and having longitudinally spaced portions for selectivelyclosing ofl? either of said end openings, thereby to selectivelyparallel the discharge of the third pump with the discharge of saidfirst and second pumps upon movement of said valve to either of saidspaced positions through the intermediate opening and the other of saidend openings, said valve having means providing a motive surface, andmeans for communicating fluid at pressures generated by said first pumpto said motive surface for moving said valve to one of said positions,and a continuous biasing means between said valve and said sleevenormally biasing said valve to the other of said positions wheneverthepressure on said motive surface is below a predetermined amount.

4. A pump comprising, acasing having three pumping cavities formedtherein,'each having an inlet and an outlet, rotary fluid displacementmeans in each of said cavities for moving fluid from a correspondinginlet to a corresponding outlet, and flow-transferring means in saidcasing selectively paralleling pairs of said outlets for directingdischarge of said pump to two separate points of utilization, saidoutlets comprising three longitudinally spaced openings, saidflow-transferring means comprising a valve member having opposed spacedapart outletcontrolling portions each respectively adapted to close oneof the end openings of said outlets, thereby paralleling the middleopening and the other end opening, and a spring between said housing andsaid valve biasing said valve to move one of said controlling portionstoward closing relation with a corresponding end opening.

5. A pump comprising, a casing having three pumping cavities formedtherein, each having an inlet and an outa valve member having opposedspaced apart outletcontrolling portions each respectively adapted toclose one of the end openings of said outlets, thereby paralleling themiddle opening and the other end opening, and a spring between saidhousing and said valve biasing said valve to move one of saidcontrol-ling portions toward closing relation with a corresponding endopening, and motive means for moving said valve in an opposite directionagainst the bias of said spring to parallel the middle opening with anopposite end opening.

6. A pump comprising, a casing having three pumping cavities formedtherein, each having an inlet and an outlet, rotary fluid displacementmeans in each of said cavities for moving fluid from a correspondinginlet to a corresponding outlet, and flow-transferring means in saidcasing selectively paralleling pairs of said outlets for directingdischarge of said pump to two separate points of utilization, saidoutlets comprising three longitudinally spaced openings, saidflow-transferring means comprising a valve member having opposed spacedapart outlet-controlling portions each respectively adapted to close oneof the end openings of said outlets, thereby paralleling the middleopening and the other end opening, and a spring between said housing andsaid valve biasing said valve to move one of said controlling portionstoward closing relation with a corresponding end opening, and motivemeans for moving said valve in an opposite direction against the bias ofsaid spring to parallel the middle opening with an opposite end opening,said motive means comprising a piston connected to said valve andmovable on the axis of said valve to impart a longitudinal thrustthereto.

7. A pump comprising, a casing having three pumping cavities formedtherein, each having an inlet and an outlet, rotary fluid displacementmeans in each of said cavities for moving fluid from a correspondinginlet to a corresponding outlet, and flow-transferring means in saidcasing selectively paralleling pairs of said outlets for directingdischarge of said pump to two separate points of utilization, saidoutlets comprising three longitudinally spaced openings, saidflow-transferring means comprising a valve member having opposed spacedapart outletcontrolling portions each respectively adapted to close oneof the end openings of said outlets, thereby paralleling the middleopening and the other end opening, and a spring between said housing andsaid valve biasing said valve to move one of said controlling portionstoward closing relation with a corresponding end opening, motive meansfor moving said valve in an opposite direction against the bias of saidspring to parallel the middle opening with an opposite end opening, saidmotive means comprising a piston connected -to said valve and movable onthe axis of said valve to impart a longitudinal thrust thereto, a rotaryshaft connected to said rotary fluid displacement means and projectingout of said casing for connection to a source of power, a flange on saidshaft adjoining one wall of said casing on the inside of said casing, athrust bearing ring carried by said casing engaging said flange andtogether with said flange forming a thrust bearing, and a sealingassembly between said casing and saidshaft and being located in saidcasing outside of said flange, said casing having recess portionsadjacent said flange vented to the inlet of the pump to flood saidthrust bearing with pumping medium for cool-ing and lubricating thethrust bearing.

8. In combination, first and second pumps each discharging to separatepoints of utilization, a third pump having a flow transferring meansreceiving the discharge thereof, each of said pumps having a common pumpcasing formed with separate pumping cavities and said casing havingformed therein a tubular bore for said flow transferring meanscommunicating with said pumping cavities, said flow-transferring meansfurther comprising a sleeve insaid tubular bore having threelongitudinally spaced openings, the end openings communicatingseparately with the separated points of utilization, the intermediateopening receiving the discharge of the third pump, a valve reciprocablyslidable in said tubular sleeve between spaced portions in said sleeveand having longitudinally spaced portions for selectively closing offeither of said end openings, thereby to selectively parallel thedischarge of the third pump with the discharge of said first and secondpumps upon movement of said valve to either of said spaced positionsthrough the intermediate opening and the other of said end openings.

9. In combination, first and second pumps each discharging to separatedpoints of utilization, a third pump having a flow transferring meansreceiving the discharge thereof, said flow transferring means comprisinga sleeve having three longitudinally spaced openings, the end openingscommunicating separately with the separated points of utilization, theintermediate opening receiving the discharge of the third pump, a valvereciprocably slidable in said tubular sleeve between spaced portions insaid sleeve and having longitudinally spaced portions for selectivelyclosing ofl either of said end openings, thereby to selectively parallelthe discharge of the third pump with the discharge of said first andsecond pumps upon movement of said valve to either of said spacedpositions through the intermediate opening and the other end openings,said valve having motive surfaces thereon responsive to pump-generatedpressures and operating to automatically position said valve in saidsleeve, thereby to parallel thefirst and third pump up to apredetermined value :ofpressure for discharge to one of the separatedpoints of utilization and operating to parallel the second and thirdpumps above said predetermined value of pressure to discharge to theother of said separated points of utilization.

10. In combination, first and second pumps each discharging to separatedpoints of utilization, a third pump having a flow transferring meansreceiving the discharge thereof, said flow transferring means comprisinga sleeve having three longitudinally spaced openings, the end openingscommunicating separately with the separated points of utilization, theintermediate opening receiving the discharge of the third pump, a valvereciprocably slidable in said tubular sleeve between spaced portions insaid sleeve and having longitudinally spaced portions for selectivelyclosing ofi either of said end openings, thereby to selectively parallelthe discharge of the third pump with the discharge of the first andsecond pumps upon movement of said valve to either of said spacedpositions through the intermediate opening in the other of said endopenings, said valve having pressure-respon- 10 sive actuating elementsfor switching the discharge from one of said pumps to the discharge ofanother of said pumps whenever the discharge pressure of said other ofsaid pumps falls below a predetermined value, thereby to insure flow offluid to the separated points of utilization.

References Cited in the file of this patent UNITED STATES PATENTS2,452,253 McGill Oct. 26, 1948 2,490,115 Clarke Dec. 6, 1949 2,506,611Neal et a1. May 9, 1950 2,554,047 Moon May 22, 1951 2,617,361 Neal Nov.11, 1952 2,620,733 Overbeke Dec. 9, 1952 2,640,423 Boyer June 2, 1953 I2,665,637 Lauck Jan. 12, 1954 2,699,724 Murray et a1. Jan. 18, 19552,780,172 Coar Feb. 5, 1957 2,823,615 Haberland Feb. 18, 1958

